I'm wondering if its getting upset at the contents of your eeprom (it is separate from the flash memory were you upload the firmware)
Its easy enough to erase the eeprom you just make a sketch to do it
Or it just didnt upload correctly, this can happen
Or your board is actually half dead, and the new firmware is triggering a fault (eg using a bit of ram unused before that doesn't work)
Its easy enough to erase the eeprom you just make a sketch to do it
Or it just didnt upload correctly, this can happen
Or your board is actually half dead, and the new firmware is triggering a fault (eg using a bit of ram unused before that doesn't work)